Association of healthy lifestyle with life expectancy free of five major disabilities in Chinese older adults

Background Whether and to what extent multiple healthy lifestyles affect the longevity of people with disabilities, including those in basic activities of daily living, mobility, vision, hearing and cognition, is crucial to policymakers. We aimed to determine the impact of combined lifestyles on life expectancy (LE) lived with and without five disabilities. Methods We recruited participants (n = 15 121 from the China Longitudinal Healthy Longevity Survey between 2008 and 2018. Healthy lifestyle levels were estimated from six factors: smoking, drinking, physical exercise, diet, cognitive activity, and sleep, which we categorised as favourable and unfavourable using the latent class growth mixture model throughout the follow-up period. We used Multi-state Markov models to assess the different disability stages of LE. Results Of the total LE at age 65, older adults with a favourable lifestyle spent 59.60% (disability-free LE (DFLE) = 10.24 years) without five disabilities in combination, whereas those with unfavourable lifestyle spent 56.74% (DFLE = 7.28 years). Furthermore, the percentage of DFLE was 64.98 (7.71 years) and 68.38 (9.91 years) in males with unfavourable and favourable lifestyle levels, respectively, and 47.92 (6.62 years) and 55.12 (10.30 years) for females. Compared to older adults with low socioeconomic status (SES) and unfavourable lifestyle level, those with lower SES and favourable lifestyle level had more 3.77 years of DFLE, those with higher SES and unfavourable lifestyle level had more 1.94 years, as well as those with higher SES and favourable lifestyle level had more 5.10 years at age 65. Corresponding associations were found separately for each of the five individual disabilities. Conclusions A favourable lifestyle level was associated with longer total LE along with a higher proportion of DFLE and may contribute to narrowing socioeconomic health inequalities. Policymakers should develop lifestyle interventions and scale up rehabilitation services in primary care, thereby delaying disabilities to later ages, especially in low- and middle-income countries.

. Baseline characteristics according to two levels of healthy lifestyle in males and females8 Table S7.Baseline characteristics according to two levels of healthy lifestyle in lower and higher SES group ..  S9.Total life expectancy and years lived without five disabilities by lifestyle level ............ 17

Details for statistical analysis
Assuming a ratio of 40%: 60% for the size of people in the favourable versus unfavourable lifestyle group, with a p-value of less than 0.05, a power of 90%, an OR of 0.7, and the disability/death rate of 30% in the favourable group [3,21], we calculated the sample size to be at least 720 for the favourable group and 1080 for the unfavourable group.
LCGMM was applied to model healthy lifestyle and SES longitudinal trajectories over the follow-up period in the older adults and to identify distinct subgroups following similar patterns.We compared two-to five-class LCGMM models iterating 1st-to 3rd-degree fractional polynomials.The best-fitting one was determined by the minimum absolute value of the bayesian information criterion (BIC), the average posterior probability (AvePP) of each subgroup not less than 0.7, the proportion of each subgroup with posterior probability greater than 0.7 not less than 0.65, and the membership of each subgroup not less than 5% of the total population (Table S3 and Table S4 in the Online Supplementary Document).Missing data for covariates were filled through multiple imputation methods (Table S5 in the Online Supplementary Document).Data were assumed to be missing at random, with predictive mean matching method used for missing continuous variables and Logistic regression model for missing binary variables.If distributed normally by the Kolmogorov-Smirnov test, continuous variables were presented as means and standard deviations; otherwise, medians and interquartile ranges were applied.Categorical variables were presented by numbers and proportions.Baseline characteristics were compared between subjects in different estimated healthy lifestyle trajectory classes using independent samples t test for continuous variables if distributed normally or Mann-Whitney U test if not, and using chi-square tests or Fisher's exact tests for categorical variables.
Population-based multistate life tables were used to calculate the total LE and years lived with and without the five major disabilities.We built a total of six multistate life tables, one with a combination of the disabilities in BADL, mobility, vision, hearing and cognition and five with individual disabilities.
To assess the association between healthy lifestyle and LE free of five major disabilities, we took into account three states (free of disability, presence of disability, and death), and four transitions between states (from non-disability to incident disability, from non-disability to mortality, from disability to mortality, as well as from disability to non-disability) in a Markov multistate transition model (Figure S 3).First, we calculated the overall transition rates for each transition using survival analysis with Gompertz distribution.Second, hazard ratios (HRs) by healthy lifestyle were calculated for each transition in Markov multistate transition models.The models were adjusted by age, gender, region, BMI, marital status, medical illnesses (hypertension, diabetes, heart disease, stroke and other cerebrovascular, and dyslipidemia), and SES.Third, we calculated proportion of lifestyle levels among the sub-study population for each transition.Finally, we combined overall transition rates, HRs and the proportion of lifestyle levels to derive weighted transition rates, which were used to create multistate life tables to calculate total LE and LE with and without disabilities for each group.The multistate life table started at age 65 years and ended at age 115 years.The 95% confidence intervals (CIs) of LE estimation were calculated using bootstrapping with 1000 iterations.Considering the pathophysiological differences between genders on lifestyle, the analysis was repeatedly stratified by gender (male and female).In addition, we conducted a joint analysis of the relationship between SES and lifestyles on the DFLE, as lower SES has a opposite impact on the DFLE.Three additional sensitivity analyses were conducted to evaluate the robustness of our findings.First, we re-performed the original analysis by including only participants whose baseline wave was 2008 (n=13138).Second, we excluded participants who already had any of the five disabilities at baseline from the 15121 participates (n=11853) and repeated the main analysis.Finally, the association of each single lifestyle factor with LE free of five major disabilities were also evaluated in models.
All statistical analysis was conducted by using R software (version 4.2.3,R Core Team, R Foundation for Statistical Computing, Vienna, Austria).The following packages were used: mice for imputing, lcmm for LCGMM, msm for Markov multistate transition models, and elect for LE estimation using multistate models.Statistical significance was defined by p<0.05 in two-sided testing.The individual is asked to follow the interviewer's instruction: "Take the paper using your right hand (1 point), fold it in the middle using both hands (1 point), and place the paper on the floor (1 point)." 3 Note: We scored each question as zero (wrong or unable to answer) or one (correct) , and the scores ranged between 0 and 30, with a higher score implying better cognitive performance.Note: Socioeconomic vulnerability index score was obtained by dividing the total score of the above variables by six, ranging from 0 to 1, with higher score indicating lower levels of socioeconomic status.19932.200 19960.810 19987.282 20007.279 19951.462 19989.765 20027.570 20060.137 19965.650 20013.868 20059.977 20100.511 Beta 19155.522 19188.895 19228.314 19267.065 19264.815 19312.919 19404.536 19496.224 19334.687 19418.438 19484.410 19609 Note: P values for all parameters in the models fitted by the maximum likelihood method were less than 0.05.

Figure S2 .Figure S3 .
Figure S2.Trajectories of healthy lifestyle and SEVI predicted by the LCGMM among 15121 older adults.The solid line represents the average blood pressure in a class and the shaded area indicated 95% CIs

Table S6 . Baseline characteristics according to two levels of healthy lifestyle in males and females
BMI: body mass index.

Table S10 . Total life expectancy and years lived with and without disability at age 65 (95%CI) by two levels of healthy lifestyle among 13138 participants at baseline in 2008
Estimated life expectancy with and without disability at age 65 according to two levels of healthy lifestyle among 13138 participants.All LEs have been calculated with hazard ratios adjusted for age, gender, region, BMI, marital status, hypertension, diabetes, heart disease, stroke/cerebrovascular disease, dyslipidemia, and SES.†Estimated life expectancy with and without disability at age 65 according to two levels of healthy lifestyle for 5651 males and 7487 females, respectively.All LEs have been calculated with hazard ratios adjusted for age, region, BMI, marital status, hypertension, diabetes, heart disease, stroke/cerebrovascular disease, dyslipidemia, and SES.‡Estimated life expectancy with and without disability at age 65 according to two levels of healthy lifestyle for 7605 lower SES and 5533 higher SES group, respectively.All LEs have been calculated with hazard ratios adjusted for age, gender, region, BMI, marital status, hypertension, diabetes, heart disease, stroke/cerebrovascular disease, and dyslipidemia.

Table S11 . Total life expectancy and years lived with and without disability at age 65 by two levels of healthy lifestyle among 11853 participants without any of the five disabilities at baseline
Estimated life expectancy with and without disability at age 65 according to two levels of healthy lifestyle among 11853 participants.All LEs have been calculated with hazard ratios adjusted for age, gender, region, BMI, marital status, hypertension, diabetes, heart disease, stroke/cerebrovascular disease, dyslipidemia, and SES.†Estimated life expectancy with and without disability at age 65 according to two levels of healthy lifestyle for 5550 males and 6303 females, respectively.All LEs have been calculated with hazard ratios adjusted for age, region, BMI, marital status, hypertension, diabetes, heart disease, stroke/cerebrovascular disease, dyslipidemia, and SES.‡Estimated life expectancy with and without disability at age 65 according to two levels of healthy lifestyle for 6750 lower SES and 5103 higher SES group, respectively.All LEs have been calculated with hazard ratios adjusted for age, gender, region, BMI, marital status, hypertension, diabetes, heart disease, stroke/cerebrovascular disease, and dyslipidemia.